something straight and long (see Molina); something straight and vertical (see Karttunen)
IPAspelling:
melɑstik
Alonso de Molina:
melaztic. cosa derecha y luenga. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 55r. col. 2. Thanks to Joe Campbell for providing the transcription.
Frances Karttunen:
MELAZTIC something straight, vertical / derecho (se dice de palo, etc.), vertcal, recto (T) [(2)Tp. 141, 175]. See MELACTIC. Frances Karttunen, An Analytical Dictionary of Nahuatl (Norman: University of Oklahoma Press, 1992), 143.